Coated articles

ABSTRACT

This application discloses non-porous substrata, such as primed and unprimed metallic surfaces and plastic surfaces, coated with a continuous adherent coating of an interpolymer composed essentially of from 0.1 to 20 weight percent of an adhesion promoting monomer which is an alkyl amino alkyl acrylamide such as N,N -dimethylaminoethyl methacrylamide with the remainder of the interpolymeric composition being made up of at least one monoethylenically unsaturated comonomer.

O i I United States Patent 1 1 1111 3,718,500 Nyquist 1 Feb. 27, 1973 54] COATED ARTICLES 3,262,985 7/1966 Muller et a] ..117/132 B x 3,374,289 3/1968 Ott et a1. ..117/161 UN X Inventor: Edwl" "Wi Mldland Mlch 3,535,293 10/1970 Anderson ..260/86.1 N x [73] Assignee: The Dow Chemical Company,

. id Mich Primary Examiner-Ralph Husack A l I Filed: Nov. 1969 stitzney Griswo d & Burdick and Albin R Lind [21] Appl. No.2 876,996

[57] ABSTRACT [52] US. Cl. ..117/132 R, 117/75, 117/124 E, This application discloses non-porous substrata, such 117/132 13, 117/132 C, 117/138 3 A, as primed and unprimed metallic surfaces and plastic ll7/138.8 F, 117/138.8 UA, 1171161 UN, surfaces, coated with a continuous adherent coating of 260/80.3 N, 260/86.1 N, 260/88.1 PN an interpolymer composed essentially of from 0.1 to [51] Int. Cl ..B32b 15/08, B32b 27/30 20 weight percent of an adhesion promoting monomer [58] Field of Search ..117/161 UN, 132 B, 132 C, whi h is an alkyl amino alkyl acrylamide such as N,N 138.8 F,l17/ 138.8 UA, 138.8 A, dimethylaminoethyl methacrylamide with the 124 E; 260/89.7 N, 86.1 N, 88.1 PN.80.3 N remainder of the interpolymeric composition being made up of at least one monoethylenically unsaturated [56] References Cited comonomer.

UNITED STATES PATENTS Dinges et a1. ..1 17/161 UN X 6 Claims, No Drawings COATED ARTICLES BACKGROUND OF THE INVENTION The coating of non-porous surfaces of solid substrata is replete with problems not the least of which is poor to no adhesion of coating to surface. This is especially true with metallic or plastic surfaces. The problem of lack of adhesion has been approached from a number of different viewpoints including formulation with functional adhesion promoting additives such as plasticizers; the physical or chemical treatment of the substratum surface; or the modification of the base polymer used in the coating composition. Included in such modifications are the incorporation into the polymer of carboxyl or other highly polar groups. Although frequently improving the adhesion those modifications usually either resulted in a reduction in some other property or in the creation of a new problem as for example corrosion of metals. Thus the ultimate in coating compositions has not been achieved to date.

The present invention is designed to improve adhesion to non-porous substrate substrata retaining the other desirable properties of the coating composition. That objective is achieved by incorporating from 0.1 to 20 weight percent of an N,N -dialkylaminoalkyl methacrylamide in the interpolymer forming the principal film forming component of the coating. This functional monomer is selected from those falling within the scope of the formula;

wherein R is hydrogen, methyl or ethyl; R, and R are selected independently from the group consisting of hydrogen, methyl, ethyl and propyl and n is an integer from 1 to 4.

A compound of the above formula is polymerized in a complementary amount of from 99.9 to 80 weight percent with one or more ethylenically unsaturated comonomers usually at elevated temperatures in the presence of a free radical catalyst. Ethylenically unsaturated comonomers copolymerizable with said dialkylaminoalkyl acrylamide or methacrylamide include vinyl aromatic monomers; esters of a,B-unsaturated acids and in particular esters of acrylic and methacrylic acid; acrylamide or methacrylamide; acrylonitrile', vinyl alkanoates, such as vinyl acetate; open chain aliphatic conjugated dienes having from four to nine carbon atoms; vinyl pyrrolidone and N-vinyl morpholine, and the like.

Suitable aromatic monomers include styrene, vinyl toluene, a-methyl styrene, the various halogenated styrenes such as p-chlorostyrene or 2,5- dibromostyrene, alkylated styrenes such as t-butyl styrene, vinyl naphthalene, and the like. Suitable acrylic esters include those having the formula wherein R is a monovalent hydrocarbon radical containing from one to about 12 carbon atoms and R is hydrogen or methyl. Suitable dienes include butadiene, isoprene, 2-halo-l ,3-butadiene wherein halo is bromine or chlorine.

When the preferred acrylate system of monomers is employed it is preferred that the polymerization be conducted in solution. By proper choice of solvent it is possible thereby to prepare the coating composition directly without isolation of the polymer and its redispersion or redissolution. Useful solvents will be readily identified. Typical are the alkyl esters, such as ethyl acetate. Alternatively the polymer may be prepared by other known polymerization methods and a useful coating composition prepared by dissolving the isolated polymer in a suitable solvent. The useful catalysts and process parameters to be used will be those conventionally employed and will depend primarily on the particular polymerization technique employed.

The polymers are soluble in a wide variety of solvents useful in the coating arts including typically the hydrocarbons, such as xylene, the esters such as ethyl acetate, the glycol ethers such as the ethyl ether of propylene glycol and mixtures of such solvents. The optimum choice of solvent will be dictated in large part by the particular comonomers used in making the polymer. .ludicious selection of such solvent will be made by simple preliminary experiment.

The amount of polymer solids used in the coating formulation will depend primarily on the application technique employed and the coating thickness desired. A spray application will require a lower viscosity solution and a lower polymer solids concentration than a brush or doctor blade technique. Thus the polymer solids concentration may vary within wide limits within the solubility parameters involved, but generally will be between about 2 to 50 weight percent solids of the combined solvent/solids weight.

Other conventional coating additives may be employed in their usual concentrations to perform their expected function. Colorants, such as dyes and pigments, fillers, stabilizers and other such additives are typical of such materials.

The coating as herein described may be applied to various non-porous substrata such as polished steel, bonderized steel, tin plate, aluminum, galvanized steel and plastic surfaces such as epoxy resins, polyesters and vinyl ester resins. The coatings will, also exhibit the desirable adhesive characteristics on vitreous surfaces such as glass. The coating thickness may be widely varied but will generally be in the range of from 0.5 to about 2.0 mils. The actual thickness will be determined by economic criteria and by the expected exposure of the coated part. When used as a primer the thickness will usually be between 0.8 to 1.2 mils to achieve optimum performance.

After coating on the substratum the coatings are preferably air dried to remove the bulk of the solvent and then baked at elevated temperatures of 200F or higher for about 30 minutes or longer. The particular drying schedule to be used will depend on the solvent employed and the coating thickness.

The inventive concept is illustrated in the following examples wherein all parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 To a l-liter flask fitted with a stirrer, reflux condenser, nitrogen inlet tube and addition funnel benzene (150 g.) ethyl acetate (120 g.) and a,a'-azodiisobu- 3. The coated article of claim 1 wherein said solid non-porous substratum is metal.

4. The coated article of claim 3 wherein said metal is steel.

tyronitrile (AIBN) (0.2 g.) were charged. This solution 5 The g ll clslm 1 wherein 531d Sohd was heated to reflux and the monomers mixed together non-pom}? S m ls p as (methyl methacrylate 195 butyl acrylate 105 g.) In addition to adheslon, the coatings were tested for with AIBN (2.0 g.) and added to the reaction flask over KPOOP Hardness by ASTMD 4474 and Salt Spray a three hour period. The monomers were purged with 10 f l The Salt Spray reslstarfce w measured nitrogen for minutes prior to their addition to the scnbmg coated Panels m two dlrecuons i Placing reaction vessel. The reaction mixture was kept under them m a 5 Percent aqueous f FP Y g a booth nitrogen throughout the course f the polymerization for 200 hours. At the end of th1s t1me the distance that o hour after the addition of the monomers was the salt spray had caused film deter1orat1on away from completed, AIBN (0.4 g.) and ethyl acetate (15 g) the scribed lines was measured in thirty secondths of an were added ThiS was repeated again zl/ h ft the 15 inch. Percent solids and viscosity were determined on addition of the monomers was completed. Heating was the non-Pigmented p y These results are continued for a total f 3 hours f h Start f the marized 1n Table ii. The film thickness varied between monomer addition 0.8 to 1.2 mils in all cases for the coated panels.-

The above polymer solut1on was formulated mm a TABLE pamt usmg the following procedure:

Sample Salt Knoop Bah Mm for 24 Hours: Number Solids Viscosity Spray Hardness 297.6 g Polymer solution (50% solids) ggz p l50.0 g TiO (Ranc) 75.0 g 2-Et hoxyethyl acetate 25 A Y'Z MFF 75.0 g Xylene A2 49.7 2, MFF 222 A3 50.0 1 ND 13.8

I This The above coating was placed on varlous substrates inv ntion with a film thickness of 0.8 1.2 mil. The coated panels 3; 28:; 15:; were allowed to stand at room temperature for 40 30 3 9, z z ND minutes and then baked at 275F for minutes. 34 ND This same procedure was employed to prepare the other polymers listed in Table I. g g ij$agz m zg The measurement of adhesion was determined using croknife. The nuthe l l gl q gi Z :1 35 Solids were determined on unpigmented polymer menca Va 0 a e are e me Viscosity was determined on unpigmented polymer using a Gardner Bubble viscometer lOO/A 10 L /d L the load in grams on the cutting point. What is claimed is: A=adhesion. 40 1. A coated article consisting essentially of a solid d= the distance between cuts in mils. non-porous substratum and an adherent coating High values of lOO/A indicate good adhesion; low thereon wherein said coating is a continuous film of an values indicate poor adhesion. interpolyme'r of from about 0.1 to 20 weight percent of TABLE I Polymer composition Adhesion to G 1- Polished Primed Poly- Alumivaniz ed Sample number MMA BA MAA S DMAEM steel steel Tin ester num steel For comparison:

A1 12.3 24.9 7.9 9. 2 8.7 NA 17. 7 25.8 24. 7 NA NA NA NA ND NA NA NA NA 20. 7 25.11 16. 6 23. 5 10. 0 13. 1 27. 6 25. 4 17. 0 26. 1 13. 1 17. 0 27. 3 30.1 21.0 19. 4 8.0 14. 2 s. 8 ND 14. 3 s. 2 0. 2 10. 4

MMA=n1otl1yl methacrylate; I3A=butyl acrylate; MAA=n1eti1acrylic acid; S=styrenc; DMAEM=dimethylaminoethyi methacrylamide; NA=n0 adhesion: ND=110t determined.

Primer was M6J40 Red Epon Resin Baking Primer produced by the Fcrbest-Sclmrndorfer Company.

wherein R is hydrogen, methyl or ethyl, R and R are selected independently from the group consisting of hydrogen, methyl, ethyl and propyl, and n is an integer from 1 to 4, and complementariiy from 99.9 to 80 weight percent of at least one ethylenically unsaturated comonomer.

2. The coated article of claim 1 wherein said adhesion promoting monomer is N,N-dimethylaminoethyl methacrylamide.

an adhesion promoting monomer within the scope of O F N(CHz)sN\ 6. The coated article of claim 5 wherein said plastic is a polyester. 

2. The coated article of claim 1 wherein said adhesion promoting monomer is N,N-dimethylaminoethyl methacrylamide.
 3. The coated article of claim 1 wherein said solid non-porous substratum is metal.
 4. The coated article of claim 3 wherein said metal is steel.
 5. The coated article of claim 1 wherein said solid non-porous substratum is plastic.
 6. The coated article of claim 5 wherein said plastic is a polyester. 